In a letter sent Tuesday to Gregory B. Jaczko, chairman of the Nuclear Regulatory Commission, representatives of the nuclear power industry argued that an enhanced safety feature designed to limit releases of radioactive gases into the environment during a severe accident was being hastily considered by the commission.

Nuclear safety advocates, however, argue that the industry is simply jockeying to avoid added costs as the commission begins to implement tougher safety guidelines for U.S. reactors in the aftermath of last year's meltdown at a Japanese power plant.

The safety feature in question -- a filter that would remove harmful radioactivity from gases being intentionally vented into the air during an emergency -- is being weighed as part of a host of new requirements for reactors in the United States. The new guidelines, formulated in response to the tsunami-driven nuclear meltdown at the Fukushima Daiichi nuclear facility in Japan last year, are aimed at shoring up a variety of safety measures at U.S. plants, including those of similar pedigree to the ones used at Fukushima.

Among the new guidelines is one that requires installation of vents in containment buildings at 31 boiling water reactors or, where they already exist, improvements to ensure their safe operation. Should all other cooling systems fail during an accident, such vents would allow operators to relieve pressure inside a reactor building by exhaling gases into the environment, thereby preventing an explosion and perhaps a far more dangerous dispersal of radioactivity.

Nuclear safety advocates have argued that installing filters on the vents -- a technology already in wide use in Europe and that is now required in Japan -- makes simple sense, because it would not only save the reactor but prevent contamination of the surrounding area. An unfiltered release could conceivably contaminate substantial swaths of land around a hobbled reactor, forcing residents and business owners to abandon an area for decades.

The NRC has so far only required the vents, though it has ordered its staff, which is developing guidelines for implementing the vent requirement, to also weigh the possibility of requiring filters.

In the letter to Jaczko, however, Anthony R. Pietrangelo, the senior vice president and chief nuclear officer with the Nuclear Energy Institute, an industry lobby group, argued that the filters should be considered separately from the vent guidelines and weighed against other means already available to control potential radioactive releases during an emergency. Among these, Pietrangelo said, are "containment sprays, flooding, venting, alternate containment heat removal, and enhanced operator actions."

In an email message, Steven Kerekes, a spokesman for NEI, elaborated on these techniques, describing them as "methods that keep or inject water into the bottom of the containment structure, that remove heat and gases from containment, and that incorporate rehearsed or trained actions by reactor operators."

Pietrangelo also said that the best way to protect people and the environment from radioactive exposures is to prevent damage to the fuel in the first place, and that the industry deploys multiple, redundant systems to do just that. "To begin the examination of enhanced mitigation strategies with a recommendation and decision on vent filters ignores these principles and the tenets of risk-informed regulation."

Nuclear safety advocates, however, argue that the industry is simply attempting to avoid added costs. "The American public should not be treated like second-class citizens by the nuclear industry and should be afforded the same level of protection provided in Europe since the late 1980s," said Jim Riccio, lead nuclear analyst with the environmental group Greenpeace. "Japan just ordered filtered vents for all their nuclear reactors and even the Romanians have followed suit," he said. "But I am still concerned that the captured commission will once again buckle and fold and side with NEI."

Two stakeholder meetings on the filter issue were held this month, and NRC staff will use that input to issue a recommendation in July.

A spokesman for Jaczko, Eliot Brenner, said in an email that "the staff continues to work on a paper to the commission on the subject, so it remains under examination."